This invention relates to a system and a method for controlling fluid flows in an oil or gas well in a geological formation, the formation including a water containing area and border surface or water level between the water containing area and a bordering volume of oil or
In oil or gas production it is a reoccurring problem that water enters the well at different positions. The water is transported to the surface together with the hydrocarbons and has to be separated at the surface. This gives extra expenses for the operator also represents a pollution problem, as the separated water has to be cleaned before it is let out into the environment.
When the water content is too large the well is closed and abandoned, even if some zones in the well may still contain oil resources. This becomes a weighting between the costs related to separating and cleaning of the water and the possible income from producing the oil. The typical degree of the exploitation of oil wells today is approximately 35%, and an improvement of only a few percent will therefore give large amounts of money for the oil companies. Thus it is a main object for this invention to obtain an improved emptying/exploitation of the reservoirs.
A number of techniques for rinsing the water at the surface are known. For example, in the U.S. Pat. Nos. 4,187,912 and 4,345,647 the use of separation tanks positioned in the well, in which the oil containing fluid is lead into the tank, and is taken out from the top of the tank. This method will be able separate some water and particles from the oil, but represents a complicated and awkward solution.
U.S. Pat. No. 5,049,037 describes a solution in which a movable pump is used to pump the oil up. The pump is kept above the oil/water surface. This also represents a complicated and awkward technique. Also, it will not be suitable for horizontal wells, in which the oil/water surface may be different along the different parts of the well, and in which the water enters the well at different positions, between the oil producing parts of the well.
As mentioned oil and gas wells penetrate several oil bearing and non-oil bearing geological formations, and it is unnecessary and expensive to close the well because significant amounts of water has entered the well in one or more parts. At the same time it is, as mentioned, expensive to separate and thereafter separate the water from the oil after it has been brought to the surface. In larger systems the production tubes from a number of wells are brought together in a manifold in which it is advantageous to detect which wells are producing, or are about to produce, water, so that they may be closed or adjusted individually.
It is an object of this invention to provide a method and a system for reducing the water production while improving the exploitation of a well at the same time as the oil production is maintained. This object is obtained with a system and a method as given above and being characterized according to the independent claims.
This way a possibility is provided for optimizing the oil or gas production in wells passing through several geological formations with varying oil/gas-levels.